convert method

@override Uint8List convert(String s)

Converts input and returns the result of the conversion.

Implementation

@override
Uint8List convert(String s) {
  var result = new Uint8List(64);
  var resultLength = 0;
  var lineNumber = 0;
  for (var line in s.split("\n")) {
    lineNumber++;

    // Remove prefix
    final match = _prefixRegExp.matchAsPrefix(line);
    if (match != null) {
      line = line.substring(match.end);
    }

    int firstGroupLength;

    // For each hexadecimal digit group
    while (true) {
      // Match hexadecimical characters
      final match = _hexRegExp.matchAsPrefix(line);
      if (match == null) {
        break;
      }
      final group = match.group(1);
      line = line.substring(match.end);

      // Validate group length
      if (group.length % 2 != 0) {
        throw new ArgumentError(
          "Error at line $lineNumber: invalid group of hexadecimal digits (non-even length): '$group'",
        );
      }
      if (firstGroupLength == null) {
        firstGroupLength = group.length;
      } else if (group.length > firstGroupLength) {
        // Longer than the first group.
        // Conclude that it's not a hex group anymore.
        break;
      }

      // Parse bytes
      for (var i = 0; i < group.length; i += 2) {
        final byteString = group.substring(i, i + 2);
        int byte;
        try {
          byte = int.parse(byteString, radix: 16);
        } catch (e) {
          throw new ArgumentError.value(
            "Error at line $lineNumber: '$byteString' is not hex",
          );
        }

        // Ensure that the buffer has capacity left
        if (resultLength == result.lengthInBytes) {
          final oldResult = result;
          result = new Uint8List(2 * resultLength);
          result.setAll(0, oldResult);
        }

        // Set byte
        result[resultLength] = byte;
        resultLength++;
      }
    }
  }
  return new Uint8List.view(result.buffer, 0, resultLength);
}